The general class of polymers of carbon monoxide and one or more ethylenically unsaturated hydrocarbons has been known for some years. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical catalysts such as benzoyl peroxide. British Patent 1,081,304 produced such polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium as catalyst. Nozaki extended the process to arylphosphine complexes of palladium. See, for example, U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and unsaturated hydrocarbons, now known as polyketones, has become of greater interest, in part because of improved methods of production. Such methods are shown by European patent applications 181,014, 121,965, 222,454 and 257,663. The disclosed processes employ, inter alia, a compound of a Group VIII metal such as palladium, an anion of a non-hydrohalogenic acid having a pKa below 2 and a bidentate ligand of phosphorus. The resulting polymers are generally high molecular weight thermoplastic polymers having utility in the production of articles such as containers for food and drink and parts for the automotive industry or structural members for use in the construction industry.
With regard to any plastic material employed in a public application, some concern must be shown for the consequences of the material catching fire and burning. Many plastics, e.g., polyvinylchloride, produce highly toxic gases upon combustion. The use of polyketones has advantages in this regard since only atoms of carbon, hydrogen and oxygen are present in the polymer molecule. Nevertheless, it would be of advantage to provide for flame retardant compositions of polyketone polymers.
Others in the past have attempted to improve the flame retardancy of polyketone compositions. For example, U.S. Pat. No. 4,761,449 discloses compositions containing a carbon monoxide/ethylenically unsaturated hydrocarbon copolymer with an alkaline earth metal carbonate, such as calcium carbonate. While these compositions show improved flame retardancy they still have certain deficiencies. In particular, the compositions containing up to 25% calcium carbonate still have Limiting Oxygen Index (LOI) values of only 27-27.5. LOI values of 30 or greater are required for many commercial applications. In addition, the mechanical properties of the flame retardant compositions must remain high if the compositions are to have commercial significance. Therefore, it is important that the amount of flame retardant necessary to obtain commercial compositions be as small as possible.